Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752624AbZGJBaw (ORCPT ); Thu, 9 Jul 2009 21:30:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751390AbZGJBam (ORCPT ); Thu, 9 Jul 2009 21:30:42 -0400 Received: from mx2.redhat.com ([66.187.237.31]:35843 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750751AbZGJBam (ORCPT ); Thu, 9 Jul 2009 21:30:42 -0400 Date: Fri, 10 Jul 2009 03:27:38 +0200 From: Oleg Nesterov To: James Morris Cc: Christoph Hellwig , David Howells , Roland McGrath , "Serge E. Hallyn" , linux-kernel@vger.kernel.org Subject: [PATCH 1/2] mm_for_maps: shift down_read(mmap_sem) to the caller Message-ID: <20090710012738.GA392@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2074 Lines: 64 mm_for_maps() takes ->mmap_sem after security checks, this looks strange and obfuscates the locking rules. Move this lock to its single caller, m_start(). Signed-off-by: Oleg Nesterov --- fs/proc/task_mmu.c | 1 + fs/proc/task_nommu.c | 1 + fs/proc/base.c | 8 +++----- 3 files changed, 5 insertions(+), 5 deletions(-) --- WAIT/fs/proc/task_mmu.c~1_MOVE_MMAP_SEM 2009-05-03 17:15:27.000000000 +0200 +++ WAIT/fs/proc/task_mmu.c 2009-07-10 02:00:56.000000000 +0200 @@ -119,6 +119,7 @@ static void *m_start(struct seq_file *m, mm = mm_for_maps(priv->task); if (!mm) return NULL; + down_read(&mm->mmap_sem); tail_vma = get_gate_vma(priv->task); priv->tail_vma = tail_vma; --- WAIT/fs/proc/task_nommu.c~1_MOVE_MMAP_SEM 2009-04-09 00:39:09.000000000 +0200 +++ WAIT/fs/proc/task_nommu.c 2009-07-10 02:01:25.000000000 +0200 @@ -189,6 +189,7 @@ static void *m_start(struct seq_file *m, priv->task = NULL; return NULL; } + down_read(&mm->mmap_sem); /* start from the Nth VMA */ for (p = rb_first(&mm->mm_rb); p; p = rb_next(p)) --- WAIT/fs/proc/base.c~1_MOVE_MMAP_SEM 2009-07-09 17:56:27.000000000 +0200 +++ WAIT/fs/proc/base.c 2009-07-10 02:05:14.000000000 +0200 @@ -235,9 +235,8 @@ static int check_mem_permission(struct t struct mm_struct *mm_for_maps(struct task_struct *task) { struct mm_struct *mm = get_task_mm(task); - if (!mm) - return NULL; - if (mm != current->mm) { + + if (mm && mm != current->mm) { /* * task->mm can be changed before security check, * in that case we must notice the change after. @@ -245,10 +244,9 @@ struct mm_struct *mm_for_maps(struct tas if (!ptrace_may_access(task, PTRACE_MODE_READ) || mm != task->mm) { mmput(mm); - return NULL; + mm = NULL; } } - down_read(&mm->mmap_sem); return mm; } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/